Pharmacotherapy of adult attention deficit hyperactivity disorder (ADHD): a meta-analysis

Our objective was to conduct a meta-analysis of therapeutic efficacy of pharmacological treatment of adult ADHD based on data from controlled clinical trials. We used the search engines PubMed and Medline to identify relevant clinical trials. Short-term studies with double-blind parallel-group design were selected for the analysis. Altogether, we identified 11 trials that met the criteria, and investigated a total of 1991 subjects, 694 and 1297 of whom were treated with placebo or active medication, respectively. In order to pool efficacy data from studies with different characteristics, including different number of participants, different trial duration and measures of efficacy, the statistical effect sizes for each study had to be calculated. Our findings showed that the pooled effect size across all treatments was in the medium-to-high range (Cohen's d=0.65, p<0.0001 vs. placebo), and the effect size for stimulants (Cohen's d=0.67, p<0.0001 vs. placebo) was somewhat higher than for non-stimulant medications (Cohen's d=0.59, p<0.0001 vs. placebo). The current database of controlled trials for adult ADHD is relatively small, and does not include data for many of the potentially important agents. In addition, effect-size estimates for different classes of medications (i.e. stimulant and non-stimulant medications) were based on separate studies; head-to-head comparisons of various agents are severely lacking. Nonetheless, results of this meta-analysis across all ADHD medications in adult subjects demonstrated statistically significant and clinically robust improvement in symptom severity compared to placebo treatment.